Symptoms: The air coming from the vents is only slightly cool or even warm. Bubbles may or may not be present in the sight glass.

Conclusion: Air or moisture may be present inside the A/C system.

Repair Procedure: When the system was recharged, it may not have put into a vacuum long enough to remove the air or boil out the moisture. It is also possible the accumulator/dryer was not replaced after the repair and has reached its moisture-absorbing capacity.

After any repair is performed, the air and moisture will need to be removed. To do this, you'll need to replace the accumulator/dryer and evacuate the A/C system, recovering any remaining refrigerant. Put the system into a vacuum for approximately 20 minutes to boil out any moisture, then recharge the system with the factory specified amount of refrigerant. Any oil that was lost should be re-added during the recharge process. Check the system's operation and performance.

Conclusion: The expansion valve could be stuck in the closed position, or the screen on the orifice tube could be clogged with debris. Check the expansion valve or orifice tube area for frosting. This area should be “sweating” condensation when the system is operating correctly.

Repair Procedure: Recover the refrigerant from the system, remove the expansion valve or orifice tube, and inspect for debris. If debris is present and the contamination is metallic, it could be coming from a failing compressor. If the contamination is black, it could be coming from deteriorating rubber hoses or desiccant from the accumulator/dryer.

If a component or line is found to be defective, replace the defective component and the accumulator/dryer. Flushing the air conditioning system can help clean blockages by dislodging sludge and debris and purging it from the system. After flushing, put the system into a vacuum for approximately 20 minutes to boil out any moisture. Then recharge the system with the factory-specified amount of refrigerant. Any oil that was lost should be re-added during the recharge process. Check the A/C system's operation and performance.

Gauge Readings: low side—55 psi (high)/high side—212 psi (normal)

4/10

Symptoms: The air from the vents is only slightly cool or warm.

Conclusion: The expansion valve could be stuck in the open position, or the capillary tube might not be making proper contact with the evaporator.

Repair Procedure: If your vehicle is equipped with a capillary tube, check to ensure that it's making contact with the evaporator. If it is, recover the remaining refrigerant from the system, and replace the expansion valve and accumulator/dryer.

Flushing the A/C system can help clean blockages by dislodging sludge and debris and purging it from the system. After flushing, put the system into a vacuum for approximately 20 minutes to boil out any moisture. Then recharge the system with the factory-specified amount of refrigerant. Any oil that was lost should be re-added during the recharge process. Check the A/C system's operation and performance.

Check out this start to finish install of a Classic Auto Air air conditioning unit in our 1964 Chevy Chevelle convertible. Only at www.chevyhiperformance.com, the official site for Chevy High Performance Magazine. » Read More